According to Consumer Reports, "DOT rules require all price advertisements for air travel to list the full price to be paid by the consumer, including all carrier-imposed surcharges."
But, as part of a campaign over the summer, "Spirit sent Twitter feeds announcing one-way fares for $9. A consumer who clicked on the link was taken to a second Webpage where the carrier disclosed for the first time that the fare did not include all taxes and fees, and that to qualify, a roundtrip ticket had to be purchased. Only after clicking on another link was the amount of additional taxes and fees disclosed."

